English: Given source and receiver traveling in inertial motion along non-intersecting paths, null frequency shift occurs for a pulse that travels the shortest distance from source to receiver. Neither emission nor receipt of this pulse occur when source and receiver are at their point of closest approach. See https://www.mathpages.com/home/kmath587/kmath587.htm
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.